A common frustration I hear when discussing the Flow hive is the amount of time it takes for the frames to fill. After some encouragement to get a good number of bees into the super (http://www.canberrabees.com/encouraging-bees-to-use-flow-frames/) it can take some time for these frames to become fully capped and ready for extraction (this is usually determined by Flow owners by viewing through the rear inspection cover).
The explanation I generally give is that ‘Flow frames are big frames, they take a long time to fill’. The thinking is that they are standard Langstroth size because they fit in a Langstroth hive/box, but the frames are longer, with limited space at each end, and they are also approximately 30% wider. This increase in dimensions adds up to a fairly substantial increase in comb volume.
The following diagram shows just how much capacity a Flow frame has, and may make you feel at ease if your bees are taking longer to fill your Flow frames than your standard Langstroth frames (click to enlarge).
The Flow frame comb dimension is ‘fixed’ at 38mm wide as the comb is plastic. The Langstroth comb dimension has been taken off an approximation of the comb width (22mm) for 35mm Hoffman end bar comb spacing.